1 /*! 2 @file 3 Defines `boost::hana::count`. 4 5 @copyright Louis Dionne 2013-2017 6 Distributed under the Boost Software License, Version 1.0. 7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) 8 */ 9 10 #ifndef BOOST_HANA_COUNT_HPP 11 #define BOOST_HANA_COUNT_HPP 12 13 #include <boost/hana/fwd/count.hpp> 14 15 #include <boost/hana/concept/foldable.hpp> 16 #include <boost/hana/config.hpp> 17 #include <boost/hana/core/dispatch.hpp> 18 #include <boost/hana/count_if.hpp> 19 #include <boost/hana/equal.hpp> 20 21 22 BOOST_HANA_NAMESPACE_BEGIN 23 //! @cond 24 template <typename Xs, typename Value> operator ()(Xs && xs,Value && value) const25 constexpr auto count_t::operator()(Xs&& xs, Value&& value) const { 26 using S = typename hana::tag_of<Xs>::type; 27 using Count = BOOST_HANA_DISPATCH_IF(count_impl<S>, 28 hana::Foldable<S>::value 29 ); 30 31 #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS 32 static_assert(hana::Foldable<S>::value, 33 "hana::count(xs, value) requires 'xs' to be Foldable"); 34 #endif 35 36 return Count::apply(static_cast<Xs&&>(xs), static_cast<Value&&>(value)); 37 } 38 //! @endcond 39 40 template <typename T, bool condition> 41 struct count_impl<T, when<condition>> : default_ { 42 template <typename Xs, typename Value> applycount_impl43 static constexpr auto apply(Xs&& xs, Value&& value) { 44 return hana::count_if(static_cast<Xs&&>(xs), 45 hana::equal.to(static_cast<Value&&>(value))); 46 } 47 }; 48 BOOST_HANA_NAMESPACE_END 49 50 #endif // !BOOST_HANA_COUNT_HPP 51